Current Trends and Challenges in RFID Part 8 doc

High Performance UHF RFID Tags for Item-Level Tracing Systems in Critical Supply Chains 201 Fig.. In the next section, a requirement analysis for a tag appositely designed to work in a

Trang 2

Current Trends and Challenges in RFID

200

Results are quite relevant: despite the very good values obtained in case of alignment, in general it emerges that no tag guarantees satisfactory performance levels in both cases and for each orientation

Fig 12 A performance comparison on the items line by varying tag type and the tag-reader antenna misalignment in presence of metals (Bomb spray)

Trang 3

High Performance UHF RFID Tags

for Item-Level Tracing Systems in Critical Supply Chains 201

Fig 13 A performance comparison on the cases line by varying tag type and the

homogenous case composition in presence of liquids and metals (ophthalmic solution)

In the next section, a requirement analysis for a tag appositely designed to work in a complex supply chain, such as the pharmaceutical one, are individuated and described and are used to drive the development of a new high performance UHF RFID tag

5 Requirements and guidelines in tags design

On the basis of the results shown in the previous sections, the realization of a tag designed ad-hoc for the specific supply chain scenario is a must Consequently, this section focuses on the analysis of the pharmaceutical supply chain peculiarities and on the individuation of the properties that a tag should own in order to guarantee high performance in all supply chain steps, even when used to track items containing electromagnetically critical materials, such

as liquids and metals It is worth observing, though, that the pharmaceutical sector is only one of the many scenarios where a similar study could be of interest

Fig 14 A performance comparison on the cases line by varying tag type and the

homogenous case composition in presence of metals (Bomb spray)

One of the sources of performance degradation in the items line is given by the potential misalignment between the NF reader antenna and the tag attached to the secondary package

Trang 4

It can be deduced, hence, that a well performing tag should guarantee at least two main lobes on the radiation pattern in every working condition, above all when it is used to trace items containing hostile materials

Another reason of reading-failure in the items line is due to the use of a FF tag antenna with

a NF reader antenna Although NF reader antennas are used in the items line, NF UHF tags cannot be used because they would not work properly in the subsequent supply chain steps, where FF reader antennas are adopted Therefore, a well performing tag should exhibit good performance both in the NF and the FF

On the items line step, the packages are read one by one and no multiple-readings related problem arises; on the contrary, they will occur in the cases line and in the border gate In such cases, shielding effects due to the presence of plenty of items as well as the potential overlapping of tags, could lead to a strong performance collapse Furthermore, also in these cases, problems due to a potential misalignment of tag and reader antennas can arise Consequently, a well performing tag should take into account such issues Therefore, the tag should be designed in order to avoid the complete tag overlapping and, moreover, it should guarantee (also in this case) multiple radiation pattern lobes

6 Design of new passive RFID UHF tags: the prototypal enhanced tag

The designed and realized Enhanced tag (patent pending number TO2010A000493) is substantially based on a dual-lobe (collapsing in a particularly oriented one-lobe) conformal label-type antenna, adaptable to the different shapes of the various item packages and easy to

be integrated in them The shape of the antenna has been modeled in order to make the complete tag overlapping highly improbable Moreover, the common design solution, based

on the use of an inner loop around the microchip, has been adopted in order to guarantee good performance also in NF condition The antenna has been realized in copper tape Cost and size are comparable with canonical general-purpose UHF tags Unfortunately, because of the patent-pending status, no details can be given on the shape and on the electromagnetic solutions adopted in order to reach the prefixed goal Nevertheless, this is not even fundamental because the primary purpose of this work is, on the contrary, to demonstrate that

an ad-hoc design of tags is able to effectively solve many of the performance degradation problems affecting general-purpose UHF tags

In Fig 15 is reported the comparison, in terms simulated horizontal plane radiation pattern, between the Enhanced tag (Fig 15a) and the commercial Thin Propeller tag (Fig 15b), when the tags are attached to a cardboard-made secondary package containing a metallic cylinder

It can be observed that the radiative behavior of the two devices is radically different

In the Thin Propeller tag case, the radiation pattern is not omnidirectional anymore and the link with the reader is possible only if the reader antenna is faced with the tag itself

On the contrary, in the Enhanced tag case, an almost 45° oriented radiation pattern is found, resulting from the combination of two mutually orthogonal lobes This way, also reader antennas orthogonal to the tag-plane can communicate with the tag

Trang 5

for Item-Level Tracing Systems in Critical Supply Chains 203

a) b)

Fig 15 Simulated horizontal radiation pattern of the a) Enhanced tag, and b) Thin Propeller tag, when they are applied on a cardboard package containing a metal block

7 Experimental results of the enhanced RFID UHF tag

In order to evaluate the effectiveness of the designed Enhanced tag in the pharmaceutical supply chain, several experimental campaigns have been performed In particular, a performance comparison of the Enhanced tag with some of the above described commercial UHF tags has been carried out in terms of successful read rate In particular, taking into account the performance analysis carried out on commercial FF and NF UHF tags, the following four tag types with higher performance have been chosen in the comparison with the Enhanced tag: Jumping Jack, Cube2, Dog Bone, and Thin Propeller One for the NF group and the others for the FF group

Experimental campaigns have been mainly focused on particular operating conditions of two steps of the pharmaceutical supply chain: the items line and the cases line As previously reported, these steps are particularly adequate to carry out an effective validation of novel RFID tags

In all tests, the speed of the conveyor belt has been set to 0.66 m/s and 0.33 m/s respectively for the items line and cases line The transmission power of the reader RFID has been set to 1W Furthermore, the RFID tag is applied on the secondary package (made of cardboard) of the medicine product Two different types of products have been used: ophthalmic solution

in aluminum sachets and metallic bomb-spray

The first part of the experimental campaign has been carried out on the items line In this test, the misalignment problem has been stressed In particular, the three different operating conditions (i.e 0°, +90°, and -90°), previously described, have been considered

The second part of the experimental campaign has been focused on the cases line In such a test, each case was composed off homogeneous items In particular, the bomb-spray case was prepared with 14 items on one layer, whereas the ophthalmic solution case was prepared with 36 items on three layers

All the results, reported in this paper, are characterized by a confidence level equal to 95% with maximum relative error of 5%

Trang 6

204

Fig 16 presents the performance comparison when a single item of ophthalmic solution, enclosed in aluminum sachets, (i.e liquid and metal) is scanned on the items line The graph clearly shows that the Enhanced tag is able to reach the optimal performance, i.e a successful read rate equal to 100%, in every critical operating conditions More in detail, the graph shows that although the performance of all tested tags are comparable under optimal conditions (orientation equals to 0°), in critical conditions (orientation equal to -90° and +90°) the performance of commercial tags decreases so abruptly to achieve in most cases a percentage of successful read rate equal to 0% Instead, the Enhanced tag reaches, also in these conditions, 100% of successful readings The results clearly show also that the NF UHF tags are not able to solve performance problems in critical operating conditions (e.g presence of misalignment)

Fig 16 A performance comparison between high-performance commercial tags and the Enhanced tag on the items line by varying the tag-reader antenna misalignment in presence

of liquids and metals (ophthalmic solution)

In Fig 17, the same performance comparison, using metallic bomb-spray, is shown The graph confirms the excellent performance achieved by the Enhanced tag in all operating conditions on the items line In this case, however, the performances obtained by some commercial tags are comparable to those reached by the realized tag (100% of successful read rate)

Fig 17 A performance comparison between high-performance commercial tags and the Enhanced tag by varying tag type and the tag-reader antenna misalignment in presence of metals (Bomb spray)

Trang 7

for Item-Level Tracing Systems in Critical Supply Chains 205 Vice versa, the second part of the tests is aimed at comparing the tags performance in another challenging step of the supply chain: the cases line Fig 18 shows the performance comparison, in terms of successful read rate, of the Enhanced tag with the four commercial tags (i.e one for NF and three for FF) by varying the composition of the ophthalmic solution case (i.e Configuration I, Configuration II and Configuration III) It is worth noting that, commercial tags have never reached successful read rate higher than 70%, while in all the configurations the Enhanced tag has achieved the maximum performance The results have also demonstrated the very poor performance of the NF UHF tags when used in a cases line Finally, Fig 19 shows the performance comparison when the case is composed of 14 items of bomb-spray In this case, only one commercial FF UHF tag (i.e Jumping Jack) presents good performance especially in Configurations I and III On the contrary, other commercial tags have shown very low performance This permits to assert that, also in this case, the Enhanced tag guarantees successful read rates better than the other tags

Fig 18 A performance comparison on the cases line between high-performance tags and the Ehnanced tag by varying the homogenous case composition in presence of liquids and metals (ophthalmic solution)

In order to further emphasize the Enhanced tag robustness also in even more critical applications, an additional test has been performed In particular, packages of milk have been considered They are characterized by an external package made in Tetra Pak, where the percentage of metal is relevant, and by the presence of liquid To test the effectiveness of the Enhanced tag, a performance comparison with one of the most powerful commercial tags (i.e Dog Bone tag) has been carried out

Also in this case, the measurement campaign has been carried out by considering both the items line (configurations 0°, +90° and -90°) and the cases line (only the configuration I with

a 3 x 3 disposition of the single milk items)

Table 2 summarizes in detail the performance comparison between Enhanced tag end Dog Bone tag in the items line and in the cases line steps considering the Tetra Pak milk package Also in this case the results are impressive: in the items line the Enhanced tag exhibits always 100% of successful read rate regardless of the package orientation The commercial Dog Bone tag, instead, shows good results only in the optimal condition In all other cases it cannot be read

Even in the cases line the Enhanced tag is much more robust than Dog Bone In fact, as can

be observed in the same Table 2, the Dog Bone is never read, whereas the Enhanced tag

Trang 8

206

achieves a successful read rate higher than 60% This clearly demonstrates the qualities in terms of robustness and reliability of the proposed Enhanced tag even in contexts different from those the tag has been designed for

Fig 19 A performance comparison on the cases line between high-performance commercial tags and the Enhanced tag by varying the homogenous case composition in presence of metals (Bomb spray)

Items line Cases line

Table 2 Performance comparison between Enhanced tag and Dog Bone tag applied on Tetra Pak package

8 Conclusion

In this chapter, the problem of the effective RFID-based traceability performed at item level has been addressed The pharmaceutical supply chain has been considered and its criticalities, in terms of kinds of goods to trace and peculiarities of the checkpoints RFID, have been individuated and discussed The inadequateness of the use of commercial general purpose tags has been proved through an exhaustive performance evaluation campaign, aimed at evaluating the successful read rate in each step of the supply chain for numerous tagged products Six different commercial Far Field UHF tags and two Near Field UHF tags have been tested; these last are the less reliable, but also the Far Field ones exhibit strong limits when used to trace products containing metals or liquids Consequently, by taking into account the traceability scenario, the requirements that a tag should own in order to overcome such limits have been individuated and, on such basis, a new enhanced tag has been realized Its performance has been rigorously evaluated and the obtained impressive results demonstrate that, if the tag is designed considering the peculiarities of the specific tracing system, a successful read rate of 100% can be obtained, regardless of the supply chain step, the composition of the traced product, and the operating conditions Finally, a very severe test has been carried out, aimed at evaluating

Trang 9

for Item-Level Tracing Systems in Critical Supply Chains 207 the performance of our Enhanced tag on Tetra Pak packets containing milk This application is one of the most challenging because of the very massive presence of both metal and liquids without any air in the middle Very surprisingly, the performance are quite good also in this case, undoubtedly demonstrating once more that when a tag is designed by taking into account the peculiarities of the tracing systems, high performance can be obtained even in particularly critical conditions

Acierno, R.; De Riccardis, L.; Maffia, M.; Mainetti, L.; Patrono, L.; Urso, E (2010) Exposure to

Electromagnetic Fields in UHF Band of an Insulin Preparation: Biological Effects, Proceeding of IEEE Biomedical Circuits and Systems Conference, Paphos, Cipro, November 2010

Aroor, S.R.; Deavours, D.D (2007) Evaluation of the State of Passive UHF RFID: An

Experimental Approach IEEE Systems Journal, vol.1, no.2, (December 2007), pp.168-176, ISSN : 1932-8184

Barchetti, U.; Bucciero, A.; De Blasi, M.; Mainetti, L.; Patrono, L (2010) RFID, EPC and B2B

convergence towards an item-level traceability in the pharmaceutical supply chain, Proceeding of IEEE International Conference on RFID-Technology and Applications, Guangzhou, China, June 2010

Bertocco, M.; Dalla Chiara, A.D.; Sona, A (2010) Performance evaluation and optimization

of UHF RFID systems, Proceeding of Instrumentation and Measurement Technology Conference, (3-6 May 2010), pp.1175-1180, ISSN: 1091-5281

Bertocco, M.; Dalla Chiara, A.; Gamba, G.; Sona, A (2009) Experimental analysis of UHF

RFID impairments and performance, Proceeding of IEEE International Instrumentation and Measurement Technology Conference, ISBN: 978-1-4244-3353-

7, Singapore, May 2009

Catarinucci, L.; Colella, R.; De Blasi, M.; Patrono, L.; Tarricone, L (2010) Improving

Item-Level Tracing Systems through Ad Hoc UHF RFID Tags, Proceeding of IEEE Radio and Wireless Symposium, New Orleans, LA (USA), January 2010

De Blasi, M.; Mighali, V.; Patrono, L & Stefanizzi, M L (2010) Performance Evaluation of

UHF RFID tags in the Pharmaceutical Supply Chain, Paper presented at The Internet of Things - 20th Tyrrhenian International Workshop on Digital Communications, Pula, Sardinia, Italy, September 2009

Finkenzeller, K (2003) RFID Handbook, Fundamentals and Applications in Contact-less

Smart Cards and Identification, Wiley & Sons, ISBN 978-0-470-84402-1

Fuschini F.; Piersanti, C.; Sydanheimo, L.; Ukkonen, L.; Falciasecca, G (2010)

Electromagnetic Analyses of Near Field UHF RFID Systems, IEEE Transaction on Antennas and Propagation, Vol 58, No 5, (May 2010) pp 1759-1770

Trang 10

208

Mirowski L et al (2009) An RFID Attacker Behavior Taxonomy IEEE Pervasive Computing

Magazine, (October-December 2009), pp.79-84, ISSN: 1536-1268

Nikitin, P V and Rao, K.V.S (2006) Performance Limitations of Passive UHF RFID

Systems, Proceeding of IEEE Antennas and Propagation Society International Symposium, Albuquerque, NM, July 2006

Rao, K.V.S.; Nikitin, P.V.; Lam, S.F (2005) Antenna design for UHF RFID tags: a review and

a practical application IEEE Transactions on Antennas and Propagation, vol.53, no.12, pp 3870- 3876, (December 2005), ISSN: 0018-926X

Ramakrishnan, K M and Deavours, D.D (2006) Performance Benchmarks for Passive UHF

RFID Tags, Proceeding of 13th GI/ITG Conference on Measurement, Modeling, and Evaluation of Computer and Communication Systems, Nurenberg, Germany, March 2006

Staake, T.; Thiesse, F.; Fleisch, E (2005) Extending the EPC network: the potential of RFID in

anti-counterfeiting, Proceeding of ACM symposium on Applied computing, ACM Press New York, NY, USA, 2005

Koo, T.W.; Kim, D.; Ryu, J.I.; Kim, J.K.; Yook, J.G.; Kim, J.C (2010) Design and

Implementation of Label-type UHF RFID Tags for the Metallic Object Application, Proceeding of IEEE Antennas and Propagation Society International Symposium, Toronto, Canada, July 2010

Thiesse, F.; Floerkemeier, C.; Harrison, M.; Michahelles, F.; Roduner, C Technology,

Standards, and Real-World Deployments of the EPC Network IEEE Internet Computing, vol.13, no.2, pp.36-43, (March-April 2009), ISSN: 1089-7801

Uysal, D D.; Emond, J P.; Engels, D W (2008) Evaluation of RFID performance for a

pharmaceutical distribution chain: HF vs UHF, Proceedings of IEEE international conference on RFID, Las Vegas, Nevada, USA, April 2008

Trang 11

Part 3

Readers

Trang 13

11

Design and Implementation of Reader Baseband Receiver Structure in a

Passive RFID Environment

Ji-Hoon Bae1, Kyung-Tae Kim2, WonKyu Choi1 and Chan-Won Park1

1Electronics and Telecommunication Research Institute

2Pohang University of Science and Technology (POSTECH)

Republic of Korea

1 Introduction

In this chapter, we present a demodulation structure suitable for a reader baseband receiver

in a passive Radio Frequency IDentification (RFID) environment RFID refers to a technology which uses radio communications to contactlessly identify a tagged physical object [1-2] An RFID system may include a plurality of electronic tags on objects, animals, and other things having unique identification information and a reader for reading or writing information from or to the tags RFID systems can be variously classified into the inductively coupled and electromagnetic schemes according to the communication method employed between an RFID reader and a tag, into an active type and a passive type according to whether the tag operates using its own power or not, and into long wave, medium wave, shortwave, ultrashort wave, and microwave depending on the frequency of the electric waves used for the communication [1-2] Essentially, a passive RFID system consists of a reader and a passive tag without a battery The International standard, ISO 18000-6C, defines the communication protocol and Ultra High Frequency (UHF) band between the reader and the passive tag [3] Many studies have been conducted in the field of UHF RFID, as described in [4-14] In the case of passive UHF RFID technology, the reader must provide the tag with continuous radio power, while the tag sends its information to the reader via a backscatter modulation The tag encodes the backscattered signal as either FM0 (bi-phase space) or Miller modulation of subcarrier at the given data rate [3] Recently, UHF Passive RFID has a trend of extending its domain to the application of an item-level-tagging (ILT) from that of a conventional pallet/case-level-tagging In the ILT RFID environment, tags can be attached on the objects composed partially of a metal or liquid and can be placed at a nearby complicated surrounding in which the metallic objects exist As a result, if undesired large signal reflected from the complicated surrounding is received at the reader receiver during receiving a desired backscattered tag signal, the performance of the identification for the reader can be easily degraded due to the reflected large signal which can leak to the reader receiver (Fig 1(a)) In addition, if insufficient isolation is guaranteed between the transmitter and receiver, the transmission power (Tx power) created by the reader transmitter can leak to the receiver (Fig 1(a)) [2] A reflected power larger than the backscattered tag signal which is generated by the return loss (S11) of the

Trang 14

212

antenna can also leak to the receiver via the circulator (Fig 1(a)) Because of these unwanted leakage components in the reader receiver, the DC-offset phenomenon can occur in the baseband of the reader receiver

Fig 1 Description of leakage components (a) and the corresponding DC-offset phenomenon (b) in a passive RFID communication environment

As a result, the received baseband signal can be corrupted by the DC-offset phenomenon (Fig 1(b)) For example, Fig 1(b) shows the Miller subcarrier signal highly affected by the

DC offset phenomenon in our reader receiver measured using an Agilent Logic Analyzer Due to the unwanted DC-offset phenomenon, the reader baseband receiver may not determine the valid bit data with sufficient reliability There have been several researches to reduce the originally generated leakage components in advance, as reported in [4-6] However, it may be difficult to perfectly and adaptively eliminate the leakage components

in the ILT RFID field, in which the performance of the reader receiver can be adversely affected by the unwanted large reflected signals Therefore, although the received baseband signal is contaminated with the DC-offset phenomenon, we attempt to further remove the DC-offset phenomenon from the distorted received signal in the baseband receiver In the earlier study, we proposed a demodulation structure composed of an edge signal generator,

an edge extractor and a signal reconstruction block for the FM0 signal distorted by the offset phenomenon [14] In this chapter, a similar concept is also applied to the reliable reconstruction of the Miller subcarrier signal not suffering from the DC-offset phenomenon

DC-by using the phase inversion information instead of the amplitude information In order to

Trang 15

Design and Implementation

of Reader Baseband Receiver Structure in a Passive RFID Environment 213

accomplish this, we detect the valid information from the corrupted signals by making use

of a demodulation structure composed of a peak signal generator, a peak detector, and a

signal reconstruction block, in order to successfully decode the received baseband signal

distorted by the DC-offset phenomenon According to the proposed demodulation method,

the peak signal is created at the position of phase inversion within the Miller subcarrier

signal sequence using the phase inversion information Therefore, although a certain

amount of DC-offset noise can be appeared in the baseband of the reader receiver, the

proposed method is allowed to supplementally deal with the DC-offset phenomenon once

Tiêu đề	Current Trends and Challenges in RFID
Chuyên ngành	RFID Technology
Thể loại	N/A
Năm xuất bản	201
Thành phố	N/A

Định dạng
Số trang	30
Dung lượng	2,96 MB